US20180161074A1 - Facet joint replacement device and methods of use - Google Patents

Abstract

A facet joint replacement device includes an enclosing element including an enclosing body and an inferior attachment member. The enclosing body includes an inner cavity defined by an interior surface of the enclosing body, wherein a portion of the interior surface of the enclosing body forms a superior articulating surface. The facet joint replacement device also includes an inferior articulating element including an articulating body and a superior attachment member. The inferior articulating body is positioned within the inner cavity of the enclosing body of the enclosing element and is configured to move within the inner cavity of the enclosing body of the enclosing element. The inferior articulating body includes an inferior articulating surface. The movement of the articulating body of the inferior articulating element is constrained in at least one direction within the inner cavity of the enclosing body of the enclosing element.

Description

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS
• Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.
• The present application is a continuation of U.S. application Ser. No. 15/472,021, entitled “FACET JOINT REPLACEMENT DEVICE AND METHODS OF USE,” filed Mar. 28, 2017, now U.S. Pat. No. 9,839,451, which claims priority benefit of U.S. Provisional Patent Application Ser. No. 62/314,634, entitled “RESTORE UNILATERAL OR BILATERAL ARTIFICIAL LUMBAR FACET JOINT SURGICAL IMPLANT,” filed Mar. 29, 2016, the entire disclosure of each of which is hereby expressly incorporated by reference.
BACKGROUNDField
• The present application relates to spinal surgery in general, and more particularly to methods, systems, and apparatuses for replacing a facet joint.
Description of the Related Art
• The lumbar facet joint is a diarthrodial synovial joint consisting of a superior articular process having a superior articular surface, an inferior articular process having an inferior articular surface, and a capsule that encloses the superior and inferior articular surfaces. Each lumbar facet joint can provide mechanical support for axial loading along the spine, facilitate movement along a longitudinal axis of the spine, and limit relative rotation and translation of adjacent vertebra. Particularly, the articular processes support compressive loading and the capsule, resists forces developed across the facet joint due to movement of the adjacent vertebrae, such as, for example, rotational and translational forces. The facet joint capsule can provide resistance to separation of the superior and inferior articular surfaces and to relative motion between the superior and inferior articular surfaces.
• Lumber facet joint dysfunction can develop as a result of degeneration, trauma, or neoplastic processes to the vertebrae and can result in spinal instability, malalignment, nerve compression, and pain, which can cause neurological deficits. Facet joint dysfunction is treated by partial or total resection of the dysfunctional lumbar facet joint. Resection can leave the addressed spinal motion segment with decreased strength, stiffness, and the ability to resist rotation.
• Fusion procedures have evolved to address the spinal de-stabilization of motion segments caused by facet joint resection. Fusion procedures result in immobilization of the two adjacent vertebrae that comprise the motion segment. As physiologic loads are transmitted across contiguous motions segments of the lumbar spine, the introduction of an immobilized motion segment within the lumbar spine can result in non-physiologic transmission of these forces. This “disconnection” within the series of motion segments that comprise the lumbar spine has been postulated to create an altered force load application on the adjacent, non-treated, motion segments, potentially accelerating the degenerative process at these locations.
SUMMARY
• Methods, systems and apparatuses are provided in certain embodiments of the present application to replace a dysfunctional facet joint.
• In one embodiment, a facet joint replacement device is provided. The facet joint replacement device includes an enclosing element including an enclosing body and an inferior attachment member. The enclosing body includes a superior end having an opening, an inferior end, and an inner cavity defined by an interior surface of the enclosing body, wherein a portion of the interior surface of the enclosing body forms a superior articulating surface. The inferior attachment member extends from the enclosing body and is configured to attach to an inferior vertebral body. The facet joint replacement device also includes an inferior articulating element including an articulating body and a superior attachment member. The inferior articulating body is positioned within the inner cavity of the enclosing body of the enclosing element and is configured to move within the inner cavity of the enclosing body of the enclosing element. The inferior articulating body includes a superior end and an inferior end forming an inferior articulating surface. The superior attachment member extends from the superior end of the articulating body and superior to the opening of the superior end of the enclosing body. The superior attachment member is configured to attach to a superior vertebral body. The movement of the articulating body of the inferior articulating element is constrained in at least one direction within the inner cavity of the enclosing body of the enclosing element.
• In another embodiment, a facet joint replacement system is provided. The facet joint replacement system includes the facet joint replacement device, an inferior fastener configured to secure the inferior attachment member to the inferior vertebral body, and a superior fastener configured to secure the superior attachment member to the superior vertebral body.
• In another embodiment, a method of implanting a facet joint replacement device is provided. The method includes providing the facet joint replacement device, securing the superior attachment member to the superior vertebral body, and securing the inferior attachment member to the inferior vertebral body.
• In another embodiment, a method of replacing a facet joint is provided. The method includes resecting at least a portion of a facet joint defined by an articular process of a superior vertebral body and an articular process of an inferior vertebral body, cannulating a pedicle of the inferior vertebral body and a pedicle of the superior vertebral body, inserting a first fastener into the pedicle of the inferior vertebral body and a second fastener into the pedicle of the superior vertebral body, and securing a facet joint replacement device to the first fastener and the second fastener, wherein the facet joint replacement device includes an enclosing body, an inferior articulating surface enclosed within the enclosing body, and a superior articulating surface enclosed within the enclosing body.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1A depicts a posterior perspective view of the facetjoint replacement device100 showing interior components in dotted lines.
• FIG. 1B depicts an anterior perspective view of the facetjoint replacement device100.
• FIG. 2A depicts a posterior perspective view of an enclosingelement102.
• FIG. 2B depicts a posterior perspective view of an inferior articulatingelement104.
• FIG. 3A depicts an anterior perspective view of the enclosingelement102.
• FIG. 3B depicts an anterior perspective view of the inferior articulatingelement104.
• FIG. 4 depicts a partial cross-sectional view of the enclosingelement102 showing a cross-section superior to a superior articulatingsurface128.
• FIG. 5 depicts a first sagittal view of the facetjoint replacement device100.
• FIG. 6 depicts a second sagittal view of the facetjoint replacement device100.
• FIG. 7 depicts a cross-sectional view of the facetjoint replacement device100.
• FIG. 8 depicts a posterior view of alumbar motion segment200.
• FIG. 9 depicts a sagittal view of thelumbar motion segment200.
• FIG. 10 depicts a posterior view of thelumbar motion segment200 with the facetjoint replacement device100 implanted.
• FIG. 11A depicts a sagittal view of thelumbar motion segment200 with the facetjoint replacement device100 implanted.
• FIG. 11B depicts a sagittal view of thelumbar motion segment200 with the facetjoint replacement device100 implanted showing components positioned within or obstructed by bone in dotted lines.
• FIG. 12 depicts a posterior view of thelumbar motion segment200 having a first facet joint replacement device100A and a second facet joint replacement device100B implanted bilaterally.
• FIG. 13 depicts a perspective view of aremovable clip300.
• FIG. 14 depicts perspective view of theremovable clip300 secured to the facetjoint replacement device100.
• FIG. 15 depicts a perspective view of aremovable clip310.
• FIG. 16 depicts a perspective view of theremovable clip310 secured to the facetjoint replacement device100.
• FIG. 17 depicts a posterior perspective view of a facetjoint replacement device400 and afastener440.
• FIG. 18 depicts an exploded view of a facetjoint replacement device500.
• FIG. 19 depicts a posterior perspective view of a facet joint replacement device600.
• FIG. 20 depicts a posterior view of themotion segment200 and amotion segment201 with a first facet joint replacement device600A and a second facet joint replacement device600B implanted ipsilaterally.
• FIG. 21 depicts a perspective view of aremovable clip320.
• FIG. 22 depicts a perspective view theremovable clip320 secured to the facet joint replacement device600.
DETAILED DESCRIPTION
• Methods, systems, and apparatuses are provided in certain embodiments of the present invention to replace a dysfunctional facet joint. In some embodiments a facet joint replacement device is provided. The facet joint replacement device can be configured to replace a facet joint that has been partially or fully resected. Following replacement, the facet joint replacement device can be configured to perform the function of a facet joint within a spinal motion segment. For example, the facet joint replacement device can include one or more components configured to perform the functions of a superior articular process, and inferior articular process, and/or a facet joint capsule. In some embodiments, the facet joint replacement device can include an enclosing element and one or more interior components positioned within an inner cavity of the enclosing element. The interior components can be configured to move within the enclosing element to facilitate movements of a spinal motion segment that simulate the movements allowed by a healthy facet joint in the human body. For example, the facet joint replacement device can allow for limited posterior/anterior motion, limited medial/lateral motion, and/or limited superior/inferior motion. The facet joint replacement device can also limit relative rotation and translation of adjacent vertebrae. For example, in some embodiments, the inner cavity of the enclosing element can be shaped and/or dimensioned to limit relative movement of the interior components within the enclosing element in at least one direction. In some embodiments, the enclosing element is shaped and/or dimensioned to limit relative movement in similar directions to a healthy facet joint capsule.
• In some embodiments, the enclosing element can include a surface configured to simulate a superior articular surface of a healthy facet joint. In some embodiments, at least one of the internal components can include a surface configured to simulate an inferior articular surface that complements of a healthy facet joint. The enclosing body can be configured to provide resistance to or otherwise limit relative disassociation and/or rotation between the surfaces configured to simulate the superior articular surface and the inferior articular surface. The enclosing body can also maintain an intraarticular environment by encapsulating the surfaces configured to simulate the superior articular surface and the inferior articular surface. For example, the enclosing cylinder can act as a physical barrier to fibrosis at the surfaces configured to simulate the superior articular surface and the inferior articular surface. The enclosing cylinder can also act as a physical barrier to prevent friction wear to the adjacent anatomy due to relative movement between the surfaces configured to simulate the superior articular surface and the inferior articular surface
• In some embodiments, a body of the enclosing element can be shaped to conform to the shape of superior and inferior articular processes and a pars interarticularis of a healthy vertebral body. The shape of the enclosing element can be configured to support axial loading in a similar manner as healthy articular processes.
• In some embodiments, at least some of the components of the facet joint replacement device can be designed such that assembly of the facet joint replacement device can be performed outside of the body. Such a facet joint replacement device can facilitate ease of implantation, as well as minimally invasive techniques.
• FIGS. 1A-7 depict a facetjoint replacement device100 according to one embodiment. The terms superior, inferior, anterior, posterior, medial, and lateral, when describing portions of the devices herein, refer to portions of the device as they are intended to be oriented with respect to the human spine.FIG. 1A depicts a posterior perspective view of the facetjoint replacement device100 showing interior components in dotted lines.FIG. 1A also includes three-dimensional coordinate axes indicating the superior (“S”), inferior (“I”), anterior (“A”), posterior (“P”), medial (“M”), and lateral (“L”) directions. As shown in the three-dimensional coordinate axes inFIG. 1A, the posterior direction P is generally pointing out of the page and the anterior direction A is generally pointing into the page. The facetjoint replacement device100 includes an enclosingelement102 and an inferior articulatingelement104 positioned at least partially within the enclosingelement102. The articulatingelement104 is referred to as an inferior articulating element because it provides a generally inferiorly facing articulating surface to engage a corresponding generally superiorly facing articulating surface on the enclosingelement102, as described further below.
• The enclosingelement102 includes an enclosingbody106 and aninferior attachment member112. The enclosingbody106 can have a generally arcuate shape configured to correspond to the shape of a pars interarticularis of a vertebra. The enclosingbody106 includes asuperior end108 and aninferior end110. Theinferior attachment member112 extends laterally from the enclosingbody106 at a segment of the enclosing body adjacent to theinferior end110. The enclosingbody106 further include an inner cavity114 (shown inFIG. 4) defined by an interior surface of the enclosingbody106 and an opening116 (shown inFIG. 2A) at thesuperior end108. A portion of the interior surface of the enclosingbody106 can be shaped to form a superior articulating surface128 (shown inFIG. 4). In some embodiments, the enclosingbody106 is configured to protect the surrounding anatomy from friction, damage, or infection due to the movement of components, including the inferior articulatingsurface126 and superior articulatingsurface128 in the interior of the enclosingbody106, for example, by acting as a physical barrier. For example, the enclosingbody106 can protect an adjacent thecal sac and adjacent nerve roots from involvement with the articulatingsurfaces126 and128 during relative movement between the articulatingsurfaces126 and128. In some embodiments, the enclosingbody106 is configured to protect the components within the interior of the enclosingbody106 from damage, wear, or fibrosis due to the surrounding anatomy, for example, by acting as a physical barrier.
• The inferior articulatingelement104 includes an articulatingbody118 and asuperior attachment member120. The articulatingbody118 is at least partially positioned within and configured to move within theinner cavity114 of the enclosingbody106. The inferior articulatingbody118 has asuperior end122 and aninferior end124. Thesuperior attachment member120 extends superior to thesuperior end122 of the articulatingbody118. In some embodiments, thesuperior attachment member120 extends through theopening116. In some embodiments, a portion of the articulatingbody118 extends superior to or in alignment with theopening116. Theinferior end124 of the articulatingbody118 forms an inferior articulatingsurface126.
• Thesuperior attachment member120 andinferior attachment member112 can be shaped and/or dimensioned to facilitate securement of the facetjoint replacement device100 to the spine. As shown inFIG. 1A, thesuperior attachment member120 andinferior attachment member112 can each be a rod. However, thesuperior attachment member120 andinferior attachment member112 can be any shape suitable for fixation directly or indirectly to a vertebral body.
• In some embodiments, the enclosingelement102 and/or the inferior articulatingelement104 can consist of or consist partially of one or more metals or metal alloys. For example, the enclosingelement102 and/or articulatingelement104 can consist of cobalt-chromium, titanium, titanium-based alloys, or any other suitable metals or metal alloys. In some embodiments, the enclosingelement102 and/orinferior element104 can be ceramic or partially ceramic. In some embodiments, the enclosingelement102 and/orinferior element104 can include super-hard ceramics.
• FIG. 1B depicts an anterior perspective view of the facetjoint replacement device100.FIG. 1B also includes three-dimensional coordinate axes indicating the superior (“S”), inferior (“I”), anterior (“A”), posterior (“P”), medial (“M”), and lateral (“L”) directions. As shown in the three-dimensional coordinate axes ofFIG. 1B, the anterior direction A is generally pointing out of the page and the posterior direction P is generally pointing into the page. As shown inFIG. 1B, the inferior articulatingsurface124 can be configured to face at least partially in an anterior direction, as well as in a generally inferior direction and a generally lateral direction.
• FIG. 1B also shows anaxis103 extending through a center point of the inferior articulating surface and anaxis105 extending through a long axis of theattachment member120. Both theaxis105 and theaxis103 have superior-inferior, lateral-medial, and posterior-anterior components.
• FIGS. 2A and 2B depicts a posterior perspective view of the enclosingelement102 and a posterior perspective view of the inferior articulatingelement104, respectively.FIG. 2A shows theopening116 through which a portion of the articulatingbody118 can extend or align with when positioned within the enclosingbody106 of the enclosingelement102.
• FIGS. 3A and 3B depict an anterior perspective view of the enclosingelement104 and an anterior perspective view of the inferior articulatingelement104, respectively. As illustrated inFIG. 3B, the inferior articulatingsurface126 can be ellipsoid or generally elliptical. The inferior articulatingsurface126 can also be convex or at least partially convex. The inferior articulatingsurface126 can be shaped and/or dimensioned to correspond to the shape, size, and/or convexity of an articular surface of a healthy inferior articular process.
• FIG. 4 depicts a partial cross-sectional view of the enclosingelement102 showing a cross-section superior to the superior articulatingsurface128.FIG. 4 shows theinner cavity114 defined by the interior surface of the enclosingbody106 and the superior articulatingsurface128. As illustrated inFIG. 4, theinner cavity114 narrows between the superior articulatingsurface128 and thesuperior end108 of the enclosingbody106. As illustrated inFIG. 4, superior articulatingsurface128 can be defined by a section of the interior surface of the enclosingbody106. The superior articulatingsurface128 can be ellipsoid or generally elliptical. The superior articulatingsurface128 can also be concave or at least partially concave. The superior articulatingsurface128 can be shaped/and or dimensioned to correspond to the shape, size, and/or concavity of an articular surface of a healthy superior articular process.
• While the inferior articulatingsurface126 and superior articulatingsurface128 are shown as elliptical inFIGS. 3B and 4, any suitable complementary surface shapes can be used. In some embodiments, the inferior articulatingsurface126 and superior articulatingsurface128 are circular or generally circular, oval or generally oval, rounded, polygonal, oblong, symmetric, asymmetric, or any other suitable shape. In some embodiments, the inferior articulatingsurface126 and superior articulatingsurface128 can be shaped such that force is applied symmetrically to the superior articulating128 when the inferior articulatingelement126 contacts or otherwise applies a force upon the superior articulatingsurface126.
• As described further herein, the articulatingbody118 is configured to move within the enclosingbody106 in at least one direction. When thesuperior attachment member120 is secured to a superior vertebral body and theinferior attachment member112 is secured to an inferior vertebral body, movement between the superior and inferior vertebral bodies can cause movement of thesuperior attachment member120 with respect to the position of the enclosingbody106 resulting from theinferior attachment member112 being secured to the inferior vertebral body. Movement of thesuperior attachment member120 with respect to the enclosingbody106 causes movement of the articulatingbody118 within the enclosingbody106 generally along the inner wall of the enclosing body. Referring again toFIG. 1B, thesuperior attachment member120 is configured to move alongaxis105 towards and away from the enclosingbody106. When thesuperior attachment member120 moves towards the enclosingbody106 along theaxis105, thesuperior attachment member120 moves along theaxis105 in a medial, anterior, and inferior direction. When thesuperior attachment member120 moves away from the enclosingbody106 along theaxis105, thesuperior attachment member120 moves along theaxis105 in a lateral, posterior, and superior direction. Thesuperior end122 of the articulatingbody118 moves along theaxis105 in the same manner when thesuperior attachment member120 moves along theaxis105. Although relative movement of thesuperior attachment member120 towards and away from the enclosingbody106 is discussed, one of skill in the art would understand that movement between the enclosingbody106 andsuperior attachment member120 could be described as movement of the enclosingbody106 towards or away from thesuperior attachment member120 or movement of the enclosingbody106 andsuperior attachment member120 towards or away from each other.
• Movement of thesuperior attachment member120 with respect to the enclosingbody106 causes movement of the inferior articulatingsurface126 along theaxis103 towards and away from the superior articulatingsurface128. The inferior articulatingsurface126 moves towards the superior articulatingsurface128 along theaxis103 when thesuperior attachment member120 moves towards the enclosingbody106, and the inferior articulatingsurface126 moves away from the superior articulatingsurface128 when thesuperior attachment member120 moves away from the enclosingbody106. When the inferior articulatingsurface126 moves away from the superior articulatingsurface128 along theaxis103, the inferior articulating surface moves along theaxis103 in a superior, posterior, and medial direction. When the inferior articulatingsurface126 moves towards the superior articulatingsurface128 along theaxis103, the inferior articulating surface moves along theaxis103 in an inferior, anterior, and lateral direction. Although relative movement of the inferior articulatingsurface126 towards and away from the superior articulatingsurface128 is discussed, one of skill in the art would understand that movement between the inferior articulatingsurface126 and the superior articulatingsurface128 could be described as movement of the superior articulatingsurface128 towards or away from the inferior articulatingsurface126 or movement of the inferior articulatingsurface126 and the superior articulatingsurface128 towards or away from each other. In some embodiments, theaxis103 extends through a center point of the superior articulatingsurface128. In some embodiments, theaxis103 extends transverse to a tangent of a center line of the inferior articulatingsurface126. Theaxis103 can represent the direction of relative movement between the articular surfaces of a healthy facet joint.
• In some embodiments, the enclosingbody106 acts to limit relative movement between the inferior articulatingsurface126 and the superior articulatingsurface128 along theaxis103. In some embodiments, the enclosingbody106 acts to limit relative movement of the inferior articlingsurface126 and superior articulatingsurface128 perpendicular to theaxis103.
• When the articulatingbody118 moves within the enclosingbody106, the inferior articulatingsurface126 can contact the superior articulatingsurface128. In some embodiments, the enclosingbody106 and inferior articulatingbody118 are configured such that a maximum distance between a center point of the inferior articulatingsurface126 and the superior articulatingsurface128 is 0.5 mm, 1.0 mm, 1.5 mm, 1.75 mm, 2.0 mm, 2.25 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 5.0 mm, less than 2.0 mm, less than 3.0 mm, less than 4.0 mm, between 1.0 mm and 3.0 mm, between 1.0 mm and 2.0 mm, between 2.0 mm and 3.0 mm, between 1.5 mm and 2.5 mm, or between 1.75 mm and 2.25 mm. In some embodiments, the superior articulatingsurface128 is shaped and/or dimensioned to receive the inferior articulatingsurface126. As shown inFIG. 4, the enclosingbody106 includes asolid portion130 between the superior articulatingsurface128 and theinferior attachment member112. In some embodiments, thesolid portion130 of the enclosingbody106 can have a depth dimensioned for receiving an axial load supplied by the articulatingbody118 to the inferior articulatingsurface126 due to movement of the articulatingbody118 within the enclosingbody106.
• FIGS. 5 and 6 show a first sagittal view showing a lateral side of the facetjoint replacement device100 and a second sagittal view showing a medial side of the facetjoint replacement device100, respectively.FIG. 7 shows a cross-sectional view of the facetjoint replacement device100 taken along line7-7 as show inFIG. 1A. As shown inFIG. 7, the interior surface of the enclosingbody106 includes a plurality of internal corners orgrooves130a,130b, and130b, each forming angle that corresponds to one of a plurality of external corners oredges132 of the articulatingbody118. Groove130bis generally positioned within the posterior side of the facetjoint replacement device100. A linear portion extends betweengroove130aandgroove130b. A second linear section extends betweengroove130cand groove130b. An arcuate section extends betweengroove130aandgroove130c. The arcuate section betweengroove130aandgroove130cis generally positioned within the anterior side of the facetjoint replacement device100. Thegrooves130 can extend along one or more portions of the interior surface of the enclosingbody106. In some embodiments, thegrooves130 extend along a length of the interior surface of the enclosingbody106 from thesuperior end108 to the superior articulatingsurface128. Theedges132 can extend along one or more portions of the outer surface of the articulatingbody118. In some embodiments, theedges132 can extend along a length of the outer surface of the articulatingbody118 between thesuperior end122 to the inferior articulatingsurface126. Thegrooves130 of the enclosingbody106 can be configured to engage theedges132 of the articulatingbody118 to prevent relative rotation of the articulatingbody118 within the enclosingbody106. The enclosingbody106 and articulatingbody118 can be shaped and dimensioned to allow for relative axial movement between the inferior articulatingsurface126 and the superior articulatingsurface128 along theaxis103.
• While threegrooves130 and threeedges132 are shown inFIG. 7, any number of grooves and edges may be utilized to prevent relative rotation of the articulatingbody118 within the enclosingbody106. One of skill in the art would recognize that the cross-sections of the inner wall of the enclosingbody106 and the outer surface of the articulatingbody118 could be any corresponding non-circular cross-sections suitable to prevent relative rotation and allow for relative translation along the length of the enclosingbody106. For example, in some embodiments, the inner wall of the enclosingbody106 and the outer surface of the articulatingbody118 can each have an oval cross-section.
• As described herein, the components of the facetjoint replacement device100 can be shaped and/or dimensioned to correspond to the anatomy of a healthy facet joint and related spinal motion segment. While lumbar facet joints are shown and described herein, applications of the facetjoint replacement device100 are not limited to the lumbar spine. In some embodiments, the facetjoint replacement device100 can be shaped and/or dimensioned to correspond to the anatomy of the thoracic spine. In some embodiments, a vertical distance between thesuperior end108 of the enclosing body and theinferior end110 of the enclosing body is between 20 mm to 44 mm, between 24 mm to 40 mm, between 28 mm and 36 mm, or between 30 mm and 34 mm. In some embodiments a vertical distance between thesuperior end108 of the enclosing body and theinferior end110 of the enclosing body is 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, or 36 mm.
• In some embodiments, one or both of the superiorarticular surface128 and inferiorarticular surface126 can have a major axis length of 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, between 10 mm to 25 mm, between 9 to 14 mm, between 10 to 14 mm, or between 12 mm to 14 mm. In some embodiments, one or both of the superiorarticular surface128 and inferiorarticular surface126 can have a minor axis length of 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, between 8 mm to 25 mm, between 8 mm to 14 mm, between 9 mm to 14 mm, or between 12 mm to 14 mm.
• In some embodiments, the superior articulatingsurface128 can be oriented at an angle of between 75° to 95° or between 55° to 85° from a transverse anatomic plane. In some embodiments, the superior articulatingsurface128 can be oriented at an angle of between −100° to −150° or between −65° to −85° from a sagittal anatomic plane. In some embodiments, the inferior articulatingsurface128 can be oriented at an angle of between 60° to 90° or between 55° to 85° from a transverse anatomic plane. In some embodiments, the superior articulatingsurface128 can be oriented at an angle of between −65° to −165° or between −65° to −145° from a sagittal anatomic plane.
• In some embodiments, an angle between theaxis103 andaxis105 can be 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, between 60° and 130°, between 70° and 120°, between 80° and 110°, between 90° and 100°, between 60° and 80°, between 80° and 100°, or between 100°, and 120°.
• In some embodiments, an angle between a plane extending through the center point of the inferior articulatingsurface126 and a plane defined by thesuperior end122 of the articulatingbody118 can be 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, between 60° and 130°, between 70° and 120°, between 80° and 110°, between 90° and 100°, between 60° and 80°, between 80° and 100°, or between 100°, and 120°.
• In some embodiments, one or both of thesuperior attachment member120 and theinferior attachment member112 can have a diameter of 1 mm, 2 mm, 3 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 8 mm, 9 mm, 10 mm, between 2 mm to 8 mm, between 4 mm to 6 mm, between 5 mm to 7 mm, or between 5 mm to 6 mm. In some embodiments, one or both of thesuperior attachment member120 and theinferior attachment member112 can have a length of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, between 2 mm to 8 mm, between 4 mm to 6 mm, between 5 mm to 10 mm, between 10 mm to 15 mm, between 15 mm to 20 mm, between 20 mm to 25 mm, between 25 mm to 30 mm, between 15 mm to 30 mm, or less than 15 mm.
• In some embodiments, a thickness of thesolid portion130 between the superior articulatingsurface128 and an inferior most point of the enclosingbody106 along theaxis103 can be 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm between 8 mm to 25 mm, between 6 mm to 14 mm, or between 8 mm to 12 mm.
• In some embodiments, the widest section of the enclosingbody106 is at the superior articulatingsurface128. The enclosingbody106 can include an inflection point at the superior articulatingsurface128. In some embodiments, the enclosingbody106 bows medially between the superior articulatingsurface128 and thesuperior end108 of the enclosingbody106. In some embodiments, the articulatingbody118 bows medially between the inferior articulatingsurface128 and thesuperior end122 of the articulatingbody118.
• FIGS. 8 and 9 depict a posterior view and a sagittal view, respectively, of alumbar motion segment200 including asuperior vertebra205, aninferior vertebra210, and anintervening disc215. Thesuperior vertebra205 includes a superiorarticular process220, an inferiorarticular process225, and a pars interarticularis230 extending between the superiorarticular process220 and the inferiorarticular process225. The pars interarticularis230 is positioned betweenlamina235 andpedicle240. Thepedicle242 is also shown. A superiorarticular process245 of theinferior vertebra210 is also shown. Anarticular surface250 of the superiorarticular process245 and anarticular surface255 of the inferiorarticular process225 align to form facet joint260, which is encapsulated by a facet joint capsule (not shown). A sagittal inclination angle of the lumbar facet joint can range between 82° to 86°. As shown inFIG. 8, the facet joint260 is located medial totransverse process265 and lateral tospinous process270. The facet joint is axially offset from the midline of the spine by between 15° to 70° degrees, dependent on the lumbar level, with more inferior lumbar segments have greater axial offset angles.
• FIGS. 10 and 11A depict a posterior view and a sagittal view, respectively, of alumbar motion segment200 with the facetjoint replacement device100 implanted. Thesuperior attachment member120 is affixed to thepedicle240 of a superior vertebra or superiorvertebral body205 by afastener274. Theinferior attachment member112 is affixed to thepedicle242 of an interior vertebra or inferiorvertebral body210 by afastener276. As shown inFIGS. 10 and 11A, thefasteners274 and276 each include a tulip head bone screw and a top loading set screw.FIG. 11B shows the positioning of the tulip head bone screws offasteners274 and276 withinpedicles240 and242 in dotted lines.
• FIGS. 10 and 11A show a unilateral implantation of a facetjoint replacement device100. One of skill in the art would understand that a facet joint replacement device, such as facetjoint replacement device100, can be implanted on either lateral side of a motion segment, or two facet joint replacement devices can be implanted bilaterally, one on each side of a particular motion segment.FIG. 12 depicts a posterior view of thelumbar motion segment200 having a first facet joint replacement device100A positioned on a first lateral side of thelumbar motion segment200 and a second facet joint replacement device100B positioned on a second lateral side of thelumber motion segment200.
• In some embodiments, a method for implanting facetjoint replacement device100 into a patient begins with the administration of general endotracheal anesthesia. Following the administration of anesthesia, the patient is placed into a prone position and intraoperative fluoroscopy is used to identify a desired location for making a skin incision for implanting the facetjoint replacement device100. After the desired location is selected, a midline lumbar-sacral incision is made at the desired location, and subperiosteal dissection is utilized to expose a desired lamina, facet joint, and entry points to cannulate the ipsilateral pedicles of the superior and inferior vertebral bodies associated with the facet joint to be replaced. In some alternative embodiments, minimally invasive surgical techniques can be employed for exposure of the desired lamina, facet joint, and entry points to cannulate the ipsilateral pedicles. After exposure of the desired structures, intraoperative fluoroscopy is utilized to confirm desired levels of exposure. After the desired levels of exposure are confirmed, a self-retaining retractor system is placed to maintain the desired level of exposure.
• After the retractor system is in place, removal of one or more sections of the facet joint and surrounding bone is performed. In some embodiments, the lamina or portion of the lamina in the motion region to be treated is removed. Removal can be performed using bone biters, angled curets, and/or bone punches. In some embodiments, a ligamentum flavum or a portion of the ligamentum flavum in the motion segment to be treated is removed. Removal of the ligamentum flavum can be performed using bone punches. The facet joint or a portion of the facet joint to be treated is also removed. Removal of the facet joint can be performed using a high speed drill, bone biters, and/or bone punches. After removal of the facet joint to be treated, further decompression of the lateral recess can be performed and adjacent nerve roots can be identified. Additional bone may be removed as necessary to prevent mechanical compression of the nerve roots.
• Following removal of the desired bone, the pedicles of the superior vertebral body and inferior vertebral body of the motion segment to be treated and desired points of entry to cannulate the pedicles are identified, for example, using intraoperative fluoroscopy. A high speed drill or bone awl is then used to perforate the cortical bone overlying the optimal entry points to cannulate each of the pedicles. The pedicles are then probed and tapped under fluoroscopic guidance. Tulip head bone screws, such as the tulip head bone screws offasteners274 and276, are then screwed into the previously tapped pedicles. Additional fixation augmentors, such as methylmethacrylate, can also be used. In some embodiments, a decision to use additional fixation augmentors is made based on apparent bone quality at the time of bone screw insertion. Methylmethacrylate or other fixation augmentors can be placed within the cannulated pedicle prior to placement of the bone screw, for example, to improve the fixation of the bone screw within the implanted pedicle bone.
• After fixation of the bone screws to the superior and inferior vertebral bodies, thesuperior attachment member120 can be placed within a receiving portion of the tulip head portion of the bone screw in the superior vertebral body, and theinferior attachment member112 can be placed within a receiving portion of the tulip head portion of the bone screw in the inferior vertebral body. After thesuperior attachment member120 andinferior attachment member112 are received within the tulip head portions of the implanted bone screws, thesuperior attachment member120 andinferior attachment member112 can be secured to the bone screws by fixation of top loading set screws to each of the tulip head portions of the implanted bone screws.
• In some embodiments, after ensuring that the implanted bone screws are in proper position and secure, but before theattachment members120 and112 are placed into the bone screws, distraction or compression can be applied between the implanted bone screws to address any asymmetric loss of the disc space height or malalignment.
• In some embodiments, facet joint replacement devices may be available in a plurality of different sizes. In such embodiments, after implantation of the tulip head bone screws into the superior and inferior vertebral bodies, a distance is measured between the tulips head portions of the bone screws and a facet joint replacement device can be selected based on the distance measured between the tulip head portions of the bone screws, for example, so that the superior and inferior attachment members of the facet joint replacement device can be securely engaged with the tulip head portions of the implanted bone screws.
• In some embodiments, facet joint replacement devices may be available with inferior articulating surfaces and superior articulating surfaces having a plurality of different angular orientations with respect to the sagittal and transverse anatomic planes, as described further herein. In such embodiments, after implantation of the tulip head bone screws into the superior and inferior vertebral body, a facet joint replacement device is selected based on the desired angular orientations of the superior articular surface and inferior articular surface. The desired angular orientations can be selected based on estimated angular orientations of the articular surfaces of a healthy facet joint in the treated motion segment.
• In some embodiments, it may desirable for inferior articulatingelement104 to reside in a particular position within the enclosingbody106 at the time of implantation into the body. For example, in some embodiments, it is desirable that the inferior articulating element is positioned within the enclosingbody106 so that the inferior articulatingsurface126 is at its closest position with respect to the superior articulatingsurface128. The position of the inferior articulatingelement104 within the enclosingbody106 can be decided based on the position of the spine during implantation of the facet joint replacement device so that the inferior articulatingsurface126 and superior articulatingsurface128 conform to the natural position of the articular surfaces of the superior and inferior articular process of the spinal motion segment to be treated.FIG. 13 depicts aremovable clip300 according to one embodiment. Theremovable clip300 includes a receivingmember302, a receivingmember304, and aconnector306 extending between the receivingmember302 and receivingmember304. Theconnector306 prevents relative movement between the receivingmember302 and receivingmember304. The receivingmember302 can be configured to removably secure to thesuperior attachment member120. The receivingmember304 can be configured to removably secure to a superior section of the exterior of the enclosingbody106.FIG. 14 depicts theremovable clip300 secured to the facetjoint replacement device100. When the receivingmember302 and receivingmember304 are secured to the facet joint replacement device, theremovable clip300 can constrain relative movement of the inferior articulatingbody118 within the enclosingbody106. In some embodiments, theremovable clip300 is metallic.
• Methods for implanting the facetjoint replacement device100 can optionally include securing theremovable clip300 to the facetjoint replacement device100 prior to implantation of the facetjoint replacement device100. After the facetjoint replacement device100 is secured to the spine, theremovable clip300 can be removed from the facet joint replacement device to allow for movement of the inferior articulatingbody118 within the enclosingbody106.
• FIG. 15 depicts aremovable clip310 according to another embodiment. Theremovable clip310 includes a receivingmember312, a receivingmember314, and aconnector316 extending between the receivingmember312 and receivingmember314. Theconnector316 prevents relative movement between the receivingmember312 and receivingmember314 and is shaped to correspond to the curvature of a side of the facetjoint replacement device100. The receivingmember312 can be configured to removably secure to thesuperior attachment member120. The receivingmember314 can be configured to secure to a section of the exterior of the enclosingbody106 near the inferior end.FIG. 16 depicts theremovable clip310 secured to the facetjoint replacement device100. When the receivingmember312 is secured to thesuperior attachment member120, theconnector316 extends along a medial side of the enclosingbody106 to the receivingmember314 at the inferior end of the enclosingbody106. The receivingmember314 can be positioned at the inferior end of the enclosingbody106 such that theremovable clip310 is secured to the facetjoint replacement device100. When theremovable clip310 is secured to the facetjoint replacement device100, theremovable clip310 can constrain relative movement of the inferior articulatingbody118 within the enclosingbody106. In some embodiments, theremovable clip310 is metallic.
• Methods for implanting the facetjoint replacement device100 can optionally include securing theremovable clip310 to the facetjoint replacement device100 prior to implantation of the facetjoint replacement device100. After the facetjoint replacement device100 is secured to the spine, theremovable clip310 can be removed from the facet joint replacement device to allow for movement of the inferior articulatingbody118 within the enclosingbody106.
• FIG. 17 depicts a posterior perspective view of a facetjoint replacement device400 and afastener440 according to another embodiment. The facetjoint replacement device400 includes many of the same or similar components as the facetjoint replacement device100 described with respect toFIGS. 1-7. The facetjoint replacement device400 includes an enclosingelement402 having an enclosingbody406 and aninferior attachment member412. The facetjoint replacement device400 also includes an inferior articulatingelement404 having an articulating body418 and asuperior attachment member420. The articulating body418 can include an articulatingsurface426, similar to articulatingsurface126. A portion of the interior surface of the enclosingbody406 can be shaped to form a superior articulating surface (not shown), similar to articulatingsurface128. The enclosingbody406 can include anopening442 configured to receive thefastener440. Theopening442 is positioned on a medial section of the enclosingbody406. In some embodiments, theopening442 is positioned on an inferior section of the enclosingbody406. In some embodiments, theopening442 is positioned on a superior section of the enclosingbody406. In some embodiments, theopening442 is positioned mid-position between a superior end of the enclosingbody406 and an inferior end of the enclosingbody406. The articulating body418 can include achannel444 configure to align with theopening442 when in a particular position or range of particular positions within the enclosingbody406 and receive thefastener440 when aligned with theopening442. The enclosing body includes achannel446 configured to align with thechannel444 of the articulating body418 when the articulating body is aligned with theopening442. Thechannel444 can be configured to receive thefastener440 when thefastener440 passes through theopening442 andchannel444. In some embodiments, thechannels444 and446 extend along an axis that is the same as, similar to, or parallel toaxis103 as described with respect toFIG. 1B. When thefastener440 is inserted into theopening442,channel444, and/orchannel446, thefastener440 moves in an inferior, anterior, and lateral direction. If thefastener440 is removed from thechannel opening442,channel444, and/orchannel446, thefastener440 moves in a superior, posterior, and medial direction.
• Thefastener440 can include threads configured to be received by complementary threads within thechannel444 andchannel446. In some embodiments, thefastener440 is a threaded screw. In some embodiments, thefastener440 is a lag screw. When received within thechannel444 and thechannel446, thefastener440 can secure the articulating body418 in a particular position within the enclosingbody406. For example, thefastener440 can secure the articulating body418 within the enclosingbody406 so that the inferior articulatingsurface426 is at its most proximal position with respect to the superior articulating surface of the enclosing body. By securing the articulating body418 in a particular position within the enclosingbody406, thefastener440 can perform a similar function to theremovable clip300.
• In some embodiments, methods of implanting the facetjoint replacement device400 include securing the articulating body418 in a desired position within the enclosingbody406 prior to implantation in the body using thefastener440. Thefastener440 can be removed after the facetjoint replacement device400 is secured to the spine. In some embodiments, thefastener440 can remain positioned within the facetjoint replacement device400 following implantation.
• In some embodiments, the depth of thefastener440 within the facetjoint replacement device400 can be altered by rotating thefastener440. In some embodiments, changing the depth of thefastener440 within the facet joint replacement device can change the distance between the inferior articulatingsurface426 and the superior articulating surface of the enclosingbody406. In some embodiments, the depth of thefastener440 can be changed after implantation to provide a different distance between the inferior articulatingsurface426 and the superior articulating surface of the enclosingbody406. In some embodiments, thefastener440 can allow for at least some movement between the inferior articulatingsurface426 and superior articulating surface of the enclosing body at least some depths of thefastener440.
• FIG. 18 depicts an exploded view of a facetjoint replacement device500 in accordance with another embodiment. The facetjoint replacement device500 includes many of the same or similar components as the facetjoint replacement device100 described with respect toFIGS. 1A-7. The facetjoint replacement device500 includes an enclosingelement502 having an enclosingbody506, aninferior attachment member512, and anopening516. The facetjoint replacement device500 also includes an inferior articulatingelement504 having an articulatingbody518 and asuperior attachment member520. The articulatingbody518 can include an inferior articulatingsurface526, similar to inferior articulatingsurface126. The inferior articulatingsurface526 can be convex. A portion of the interior surface of the enclosingbody506 can be shaped to form a superior articulating surface (not shown), similar to articulatingsurface128. The superior articulating surface of the facetjoint replacement device500 can be concave. The facetjoint replacement device500 further includes aveneer550 configured to be positioned between the inferior articulatingsurface526 and the superior articulating surface of the facetjoint replacement device500. In some embodiments, the veneer has a thickness of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, between 1 mm and 3 mm, between 1 mm and 2 mm, or between 2 mm and 3 mm. Theveneer550 can include a low friction material, such as high molecular weight polyethylene. In some embodiments, the veneer is formed of vitamin E impregnated polyethylene, which may function as a free radical scavenger. Theveneer550 can reduce friction and wear between the inferior articulatingsurface526 and the superior articulating surface of the facetjoint replacement device500. In some embodiments, theveneer550 includes a concave side configured to engage the inferior articulatingsurface526. Theveneer550 can also include a convex side configured to engage the superior articulating surface of the facetjoint replacement device500. In some embodiments, theveneer550 can be secured to the inferior articulatingsurface526. In some embodiments, theveneer550 can be secured to the inferior articulatingsurface526 by a fastener, such as a screw. In an alternative embodiment, theveneer550 can be formed as part of a sleeve configured to fit over at least a portion of the articulatingbody518 including the inferior articulatingsurface526.
• FIG. 19 depicts a posterior view of a facet joint replacement device600 according to another embodiment. The facet joint replacement device600 includes many of the same or similar components as the facetjoint replacement device100 described with respect toFIGS. 1A-7. The facet joint replacement device600 includes an enclosingelement602 having an enclosingbody606 and aninferior attachment member612. The facet joint replacement device600 also includes an inferior articulatingelement604 having an articulatingbody618 and asuperior attachment member620. The articulatingbody618 can include an articulating surface (not shown), similar to articulatingsurface126. A portion of the interior surface of the enclosingbody606 can be shaped to form a superior articulating surface (not shown), similar to articulatingsurface128. Theinferior attachment member612 includes ahole613 and atextured surface615. Thesuperior attachment member620 includes ahole621 and atextured surface623. Theholes613 and621 can each receive a fastener, such as a threaded bone screw, to secure the facet joint replacement device600 to the spine.
• The shape of theinferior attachment member612 allows for alignment of theinferior attachment member612 with a superior attachment member of a facet joint replacement device positioned to replace a facet joint at an inferior contiguous vertebral body. The shape of thesuperior attachment member620 allows for alignment of thesuperior attachment member620 with an inferior attachment member of a facet joint replacement device positioned to replace a facet joint of a superior contiguous vertebral body.
• FIG. 20 depicts a posterior view of themotion segment200 and amotion segment201 with a facet joint replacement device600A and a facet joint replacement device600B implanted ipsilaterally. The facet joint replacement device600A is positioned to replace the facet joint260 of themotion segment200. The facet joint replacement device600B is positioned to replace a facet joint of themotion segment201, which is inferior tomotion segment200 and includesvertebral body210,vertebral body207, andintervertebral disc217. The facet joint replacement devices600A and600B include the same components as the facet joint replacement device600 described herein. The facet joint replacement device600A includes a superior attachment member620A and an inferior attachment member612A, each having a hole and a textured surface. The facet joint replacement device600B includes a superior attachment member620B and an inferior attachment member612B, each having a hole and a textured surface. The superior attachment member620A is secured to the superiorvertebral body205 by afastener674 passing through the hole of the superior attachment member620A. The inferior attachment member612A is positioned so that the hole of the inferior attachment member612A aligns with the hole of the superior attachment member620B. The textured surfaces of the attachment members612A and620B can contact one another to provide friction or otherwise constrain movement of the attachment members612A and620B relative to one another once aligned. Afastener676 extends through both the hole in the attachment member612A and the hole in the attachment member620B to secure the attachment members612A and620B to the inferiorvertebral body210. Afastener678 extends through the hole of the inferior attachment member612B to secure the attachment member612B tovertebral body207. In some embodiments, each of thefasteners674,676, and678 can include a bone screw and/or a threaded locking nut.
• Methods of implanting facet joint replacement devices600A and600B can include aligning the opening of the inferior attachment member612A with the opening of the superior attachment member620B and securing the inferior attachment member612A and the superior attachment member620B to the same vertebral body by extending a fastener through the opening of the inferior attachment member612A device and the opening of the superior attachment member620B.
• FIG. 21 depicts aremovable clip320 according to another embodiment. Theremovable clip320 includes a hook member322, a receivingmember324, and aconnector326 extending between the hook member322 and receivingmember324. Theconnector326 prevents relative movement between the receiving member322 and receivingmember324 and is shaped to correspond to the curvature of the posterior of the facet joint replacement device600. The hook member322 can be configured to removably secure to thesuperior attachment member620. The receivingmember324 can be configured to secure to a section of the exterior of the enclosingbody606 near the inferior end.FIG. 22 depicts theremovable clip320 secured to the facet joint replacement device600. When the hook member322 is secured to thesuperior attachment member620, theconnector326 extends along a posterior section of the enclosingbody606 to the receivingmember324 at the inferior end of the enclosingbody606. The receivingmember324 can be positioned at the inferior end of the enclosingbody606 such that theremovable clip320 is secured to the facet joint replacement device600. When theremovable clip320 is secured to the facet joint replacement device600, theremovable clip320 can constrain relative movement of the inferior articulatingbody618 within the enclosingbody606. In some embodiments, theremovable clip320 is metallic.
• Methods for implanting the facet joint replacement device600 can optionally include securing theremovable clip320 to the facet joint replacement device600 prior to implantation of the facet joint replacement device600. After the facet joint replacement device600 is secured to the spine, theremovable clip320 can be removed from the facet joint replacement device to allow for movement of the inferior articulatingbody618 within the enclosingbody606.
• While this invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention. For all of the embodiments described above, the steps of the methods need not be performed sequentially.
• Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic that departs from exactly parallel by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, 0.1 degree, or otherwise.
• It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention.

Claims (21)

1. A facet joint replacement system, comprising:

a facet joint replacement device comprising:

an enclosing element comprising:

an enclosing body comprising:

a superior end having an opening;

an inferior end; and

an inner cavity defined by an interior surface of the enclosing body, wherein a portion of the interior surface of the enclosing body forms a superior articulating surface; and

an inferior attachment member extending from the inferior end of the enclosing body, the inferior attachment member configured to be fixed with respect to an inferior vertebral body; and

an inferior articulating element comprising:

an articulating body positioned within the inner cavity of the enclosing body of the enclosing element, the articulating body configured to move within the inner cavity of the enclosing body of the enclosing element, wherein the articulating body comprises:

a superior end;

an inferior end forming an inferior articulating surface; and

a superior attachment member extending from the superior end of the articulating body and superior to the opening of the superior end of the enclosing body, the superior attachment member configured to be fixed with respect to a superior vertebral body.

2. The facet joint replacement system ofclaim 1, wherein the enclosing body of the enclosing element tapers from the inferior end of the enclosing body to the superior end of the enclosing body.

3. The facet joint replacement system ofclaim 1, wherein the articulating body of the inferior articulating element tapers from the inferior end of the articulating body to the superior end of the articulating body.

4. The facet joint replacement system ofclaim 1, wherein the enclosing body of the enclosing element bows medially between the superior articulating surface and the superior end of the enclosing body.

5. The facet joint replacement system ofclaim 1, wherein the articulating body of the inferior articulating element bows medially between the inferior articulating surface and the superior end of the articulating body.

6. The facet joint replacement system ofclaim 1, wherein the inferior attachment member and superior attachment member each comprise an attachment rod.

7. The facet joint replacement system ofclaim 1, wherein the inferior attachment member and superior attachment member each comprise a hole configured to receive a fastener.

8. The facet joint replacement system ofclaim 1, wherein the inferior articulating surface of the articulating body is configured to translate relative to the superior articulating surface of the enclosing body along an axis extending through the inferior articulating surface and the superior articulating surface.

9. The facet joint replacement system ofclaim 1, wherein one or both of the enclosing element and the inferior articulating element comprise one or more metals or metal alloys.

10. The facet joint replacement system ofclaim 9, wherein the one or more metals or metal alloys comprise on or more of cobalt-chromium and titanium based alloys.

11. The facet joint replacement system ofclaim 1, wherein movement of the articulating body of the inferior articulating element is constrained in at least one direction within the inner cavity of the enclosing body of the enclosing element.

12. The facet joint replacement system ofclaim 1, wherein one or both of the enclosing element and the inferior articulating element comprise a ceramic.

13. The facet joint replacement system ofclaim 1, wherein the inferior articulating surface of the articulating body is convex.

14. The facet joint replacement system ofclaim 1, wherein the superior articulating surface of the enclosing body is concave.

15. The facet joint replacement system ofclaim 1, wherein at least a portion of the interior surface of the enclosing body comprises one or more grooves, wherein at least a portion of articulating body comprises one or more edges configured to slide within the one or more grooves of the interior surface of the enclosing body.

16. The facet joint replacement system ofclaim 15, wherein the one or more grooves of the interior surface of the enclosing body are shaped to constrain rotational motion of the articulating body within the enclosing body.

17. The facet joint replacement system ofclaim 1, further comprising a veneer positioned between the inferior articulating surface of the articulating body and the superior articulating surface of the enclosing body.

18. The facet joint replacement system ofclaim 17, wherein the veneer comprises a low friction material.

19. The facet joint replacement system ofclaim 17, wherein the veneer comprises high molecular weight polyethylene.

20. The facet joint replacement system ofclaim 17, wherein the veneer comprises a concave side configured to engage the inferior articulating surface of the articulating body and a convex side configured to engage the superior articulating surface of the enclosing body.

21-30. (canceled)

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